1. Field of the Invention
The invention relates to a method for removal of unwanted foulants from monomers, during monomer preparation, and purification.
2. Description of the Prior Art
Much work has been conducted on the development of additives which may be added to the distillation trains of hydrocarbon processing units to prevent fouling. "Fouling" is often the result of dimer, trimer and polymer formation of the hydrocarbon being distilled. Materials added to prevent fouling have generally been materials that can be categorized as anti-foulants or polymerization inhibitors. Many of these anti-foulants and polymerization inhibitors carry over in the distillation process and great care must be taken to ensure that final product does not contain residual quantities of these materials since they may interfere with the distillates ultimate use.
It would accordingly be a benefit to the art of distillation of reactive hydrocarbons if a method could be found which would eliminate or minimize the use of chemical anti-foulants and polymerization inhibitors. The subject invention which is related to the use of non-solvent precipitating agents provides such a benefit.
Non-solvent precipitation may be defined as the use of a hydrocarbon solvent, or mixtures of hydrocarbon solvents to cause the precipitation of a material to which the non-solvent is mixed while leaving other materials present soluble. This type of technique has been utilized to separate and purify polymers from a system in laboratory scale operations. An example of this technique would be the addition of an aqueous polymer solution of polyacrylamide to a non-solvent of isopropyl alcohol. In this instance, the polymer is precipitated in the alcohol water solution while low molecular weight materials remain solubilized and can be removed.
Non-solvent precipitation may also be utilized in techniques for the determination of molecular weights of polymers, to examine the loss of solvency of crude oil as fractions are removed by distillation. The precipitation of insoluble materials from a non-solvent is a well known phenomenon.